As someone pointed out in the comments, these figures ignore self-published ebooks that don't have ISBNs and thus don't show up in Nielsen, BookScan, etc.
Most U.S. self-published ebook authors don't use ISBNs because they're outrageously priced in small quantities, and none of the major ebook outlets (Amazon, B&N, Apple) require them. The situation is somewhat different in other countries, where ISBNs are issued by government agencies for free.
These books are a substantial portion of Amazon's ebook sales, the majority in some genres.
For a more comprehensive take on sales numbers, see:
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[ 2.9 ms ] story [ 15.1 ms ] threadMost U.S. self-published ebook authors don't use ISBNs because they're outrageously priced in small quantities, and none of the major ebook outlets (Amazon, B&N, Apple) require them. The situation is somewhat different in other countries, where ISBNs are issued by government agencies for free.
These books are a substantial portion of Amazon's ebook sales, the majority in some genres.
For a more comprehensive take on sales numbers, see:
http://authorearnings.com/